A sheriff's deputy will not face any charges for fatally shooting a teen-ager who pointed a toy gun at him, the San Bernardino County district attorney's office announced. The decision followed a review of the April 7 shooting of Leonard Joseph Falcon, 19, in Rancho Cucamonga. Falcon was shot because the deputy, Dan'l Durrant, 30, mistook the toy for a real weapon during a nighttime encounter at a school where the victim was playing a game called Lazer Tag. "The deputy involved was justified in believing that his life was in danger and that his self-defense required the use of deadly force," said a statement issued by District Atty. Dennis Kottmeier's office. The victim's father, Joseph Falcon, said he had no comment, " . . . because I expected just exactly what they said."